TIJUANA, Mexico – The Mexican border city of Tijuana, a weekend playground for U.S. visitors, plans to give prostitutes electronic health cards and regulate brothels in an effort to clean up its gritty image.

Under a bylaw passed last month, the city is forcing about 50 clandestine brothels to meet public safety and hygiene standards, like putting clean sheets on beds, or face closure.

“We have a lot of prostitution but few controls,” Martha Montejano, head of the council’s health and human development commission, said on Wednesday. “This aims to combat sexually transmitted diseases and bring order to the massage parlors.”

Prostitution is illegal in Mexico but brothels are often left alone by law enforcement agents.

Under the regulation, some 7,000 male and female sex workers in Tijuana, a city of 1.2 million people, will carry health cards with a computer chip to show they have passed monthly health checks.

The Tijuana bylaw is due to come into force in the coming days, perhaps as early as Friday, and a team of 30 inspectors already has begun visits to brothels, which are often thinly disguised as massage parlors.

The bylaw is the first serious attempt to regulate the sex trade in the city, which has served as a playground of bars, brothels and racetracks for visitors from California since the U.S. prohibition era in the 1920s.

Brothel operators back the measure, which they say allows them to operate in the open for the first time, while providing safeguards for both sex workers and clients.

“It makes it safer for everyone involved,” a brothel manager called Jorge told Reuters at a massage parlor close to Avenida Revolucion, a strip of gaudy tourist bars. “The girls and the clients are better off and it means the authorities can’t close us down if we comply.”

The Tijuana bylaw, similar to regulations in cities like Monterrey and the Pacific coast resort of Acapulco, has been criticized by some opposition councilors.

“It’s like throwing up your hands and saying that we’ve been beaten by the problem of prostitution,” said opposition councilor Luis Ledezma of the conservative National Action Party. “We think it definitely goes too far.”